1. Field of the Invention
The present invention relates to an illumination apparatus for microscope, and a microscope using the same.
2. Description of the Related Art
In recent years, a field called optogenetics has been showing a widespread expansion. Moreover, in an observation of a biological specimen, a fluorescence recovery after photobleaching (FRAP) has been used widely as a conventional observation method. In an observation in optogenetics, and an observation by the fluorescence recovery after photobleaching, sometimes light is irradiated only to a part of the specimen, such as a cell. In the cell to which the light has been irradiated, there occurs a change due to the light irradiated becoming a stimulus. Moreover, in a case in which, there is a cell around the cell to which the light has been irradiated, sometimes there occurs a change also in the cell which is around the cell to which the light has been irradiated. Therefore, at the time of observation, one entire cell, or a plurality of cells is illuminated. In such manner, in the observation by the fluorescence recovery after photobleaching, and in the observation by the optogenetics, an illumination area for imparting stimulus and an illumination area for making observation, differ.
Moreover, in a case in which, there is a plurality of objects to be stimulated, it is necessary to illuminate a plurality of locations which are separated spatially, and it is necessary to control an illumination time individually for each location, according to the number of objects and a position.
As an illumination apparatus in which, it is possible to set the illumination area, the illumination position, and the illumination time, an illumination apparatus disclosed in Japanese Patent Application Laid-open Publication No. 2011-118371 and an illumination apparatus disclosed in Japanese Patent No. 4425098 are available.
In the illumination apparatus described in Japanese Patent Application Laid-open Publication No. 2011-118371, light from a light source is irradiated to a specimen via a digital micro mirror device (hereinafter, referred to as ‘DMD’). The DMD is a device having a plurality of micro mirrors, and the micro mirrors are disposed two-dimensionally. The illumination area, the illumination position, or the illumination time is changed by changing a direction of each micro mirror.
In the illumination apparatus described in Japanese Patent No. 4425098, light from a light source is irradiated to a specimen via a spatial light modulation element. Moreover, a device having a liquid crystal, or the DMD, has been used as the spatial light modulation element. This device having the liquid crystal has a plurality of micro areas having the liquid crystal, and these micro areas are disposed two-dimensionally.
Moreover, in the illumination apparatus described in Japanese Patent No. 4425098, a surface of the spatial light modulation element is disposed to be inclined with respect to a specimen surface. Here, if the spatial light modulation element is let to be conjugate with the specimen plane, a projection plane of the spatial light modulation element intersects with the specimen plane. In this case, a portion other than an intersecting portion is not subjected to a focused illumination. Therefore, in the illumination apparatus described in Japanese Patent No. 4425098, the spatial light modulation element is considered to be an element which is disposed at a pupil position of an optical system.
FIG. 5A and FIG. 5B are diagrams showing an arrangement of the DMD and the optical system. FIG. 5A is a diagram showing a structure of the DMD. As shown in FIG. 5A, a DMD 700 has a plurality of micro mirrors 701. Moreover, the micro mirrors 701 are disposed two-dimensionally. Here, the micro mirror 701 oscillates through a predetermined angle around an axis, with a diagonal 702 as an axis. By the oscillation of the micro mirror 701, the micro mirror 701 changes a direction of a mirror surface.
Generally, light is irradiated to the DMD 700 via the optical system. A direction of incidence of light is a direction orthogonal to the diagonal 702 as shown by an arrow mark in FIG. 5A. In this case, the optical system is positioned obliquely downward or obliquely upward with respect to the DMD 700. Therefore, it is not possible to dispose the DMD 700 and the optical system in the same plane.
FIG. 5B is a diagram showing an arrangement of the DMD and the optical system. Illumination light Lin is incident on the DMD 700 via an optical system 703. The illumination light Lin is reflected at the micro mirrors 701 of the DMD 700, and is emerged from the DMD 700 as illumination light Lout. The illumination light Lout emerged from the DMD 700 reaches a specimen via an optical system 704.
In FIG. 5B, a traveling direction of the illumination light emerged from the DMD 700 is a normal direction of a surface of the DMD 700. For making such an arrangement, it is indispensable to make an angle of incidence of the illumination light Lin on the DMD 700 small. It is necessary to dispose the optical system 703 in a direction inclined with respect to the DMD 700. An angle of the optical system 703 with respect to the DMD 700 corresponds to an angle through which the micro mirror 701 oscillates. Here, when a position of the optical system 703 is near the DMD 700, the illumination light Lout is incident on the optical system 703, and the optical system 703 and the optical system 704 make a contact. To avoid this, it is preferable to keep the optical system 703 and the optical system 704 at a distance from the DMD 700. However, when the optical system 703 and the optical system 704 are kept at a distance from the DMD 700, a size of the illumination apparatus becomes large.
Moreover, as it has been mentioned above, the optical system 703 is positioned at an obliquely upward position, or at an obliquely downward position. Therefore, a position adjustment of the DMD 700 and the optical system 703 becomes complicated. Moreover, an efficiency of light in the DMD 700 is low.